The invention relates to digital tape drive storage devices, and in particular, to a method and apparatus for preventing disconnection failures in a single reel tape drive.
Digital data is stored on tape drives utilizing a variety of designs, but in all cases, magnetic tape media is wound between a pair of tape reels as data is transferred to or from the tape media. In the art of data storage, the physical space required to store data is an important concern. To conserve space, tape drives often use a single reel tape cartridge design, which utilizes a supply reel located within a removable tape cartridge and a takeup reel located within the tape drive.
After the tape cartridge is inserted into the tape drive, the tape media must be loaded into the tape drive. The loading operation includes connecting the tape media to the takeup reel and winding the tape media to a start point or read position. Various methods have been employed to make this connection. FIG. 1 illustrates one such method wherein the tape media connects to the takeup reel via a buckle 100 between a tape cartridge leader 103 and a takeup leader 101. The tape cartridge leader 103 terminates the tape media at one end and is a strong flexible plastic strip that includes an ovular aperture 102 configured to mate with the takeup leader 101. The takeup leader 101 is a similar strong flexible plastic strip attached at one end to the takeup reel. The opposing end includes a stem 104 and a tab 105 designed to buckle with the ovular aperture 102 on the tape cartridge leader 103. During the buckling operation, a rotating catch connected to a load motor cooperates with a positioning lever to position the takeup leader 101 and the tape cartridge leader 103 for buckling. After the takeup leader 101 and the tape cartridge leader 103 are buckled, the catch is rotated out of the way to a loaded position and the buckle 100 is wound through a tape path until the tape media is in a read position relative to the tape head. Similarly, an unloading operation includes unwinding the takeup leader 101 and tape cartridge leader 103 back past the tape head, rotating the catch back to the unloaded position to disconnect the takeup leader 101 and the tape cartridge leader 103, and ejecting the tape cartridge from the tape drive.
Unfortunately, failures that cause the tape drive to malfunction can occur during the unloading operation. One form of failure, referred to as a disconnection failure, occurs when the catch does not completely rotate back to the unloaded position prior to ejection of the tape cartridge. When this occurs, the buckle between the tape cartridge leader 103 and the takeup leader 101 does not disconnect causing the tape cartridge to become stuck halfway in the tape drive when an ejection is attempted. Following a disconnection failure, the tape drive is rendered inoperable and must be removed from its"" enclosure for service. If the tape cartridge is forced out of the tape drive, the tape cartridge leader 103, the takeup leader 101 and/or the tape media are frequently damaged.
Also, unfortunately, this problem is not easily solved without redesigning the entire tape drive. The operation of the catch and the cartridge ejection lever, which retains the tape cartridge in the tape drive, are mechanically tied to a single load motor through a gear train. During operation, the load motor uses a cam to release the catch and allow the catch to rotate from the loaded position to the unloaded position under the force of a first spring. The load motor operation is then continued without interruption until the cam triggers the cartridge release lever and ejects the tape cartridge from the tape drive under the force of a second spring. Under normal operating conditions, the gear train provides the necessary timing to rotate the catch to the unloaded position prior to triggering the cartridge release lever. However, because the speed of the load motor is affected by wear, line voltage, torque constant and other factors, the timing is difficult to maintain. The problem is further compounded by wear in the mechanical components of the catch as well as debris build up at the pivot point that alter the rotation speed of the catch.
The present invention overcomes the problems outlined above and advances the art by providing a sensing assembly that prevents disconnection failures from rendering the tape drive inoperable. More particularly the sensing assembly detects the status of the tape cartridge leader and takeup leader disconnection prior to ejecting the tape cartridge from the tape drive. If the leaders are not disconnected, the tape drive is automatically reset for a retry operation prior to ejecting the tape cartridge.
Advantageously, the present sensing assembly determines the status of the buckle connection before the tape cartridge is ejected. If the buckle connection is not completely disconnected a retry operation is performed, and the sensing assembly again provides the status of the buckle connection before the tape cartridge is ejected. Only after a positive determination that the buckle connection is disconnected, will the tape cartridge be ejected from the tape drive. Also advantageously, users are pre-warned of required service or pending drive failures before a tape cartridge with important data becomes stuck in the tape drive.
The sensing assembly comprises a microprocessor, a cam, and a position sensor that provide feedback on the disconnection status of the buckle between the takeup leader and the tape cartridge leader. The microprocessor uses the position sensor to detect a first position and a second position of the takeup leader in the tape path. The microprocessor uses the movement between the first and second positions to determine if the takeup leader and the tape cartridge leader are disconnected prior to ejecting the tape cartridge. The cam permits the load motor operation to be briefly paused during the sensing.